Researchers have uncovered a 7.2-million-year-old femur in Bulgaria that shows features suggesting bipedal walking, predating known African hominin fossils. The find, linked to the ape species Graecopithecus freybergi, challenges the idea that upright walking evolved solely in Africa. However, experts caution that more evidence is needed to confirm bipedality.
In 2016, a team led by Madelaine Böhme from the University of Tübingen in Germany excavated a nearly complete right thighbone, or femur, at the Azmaka site near Chirpan in southern Bulgaria. The bone, measuring 21.5 centimetres and nicknamed “Diva,” comes from sediments dated to 7.2 million years ago, making it older than any recognized hominin fossils from Africa.
Böhme's group analyzed the femur using measurements and a CT scan, identifying traits they interpret as signs of bipedalism. These include a short neck with a straight section for vertical loads, thicker bone on the lower neck to bear weight, and a ridge for gluteal muscles that help maintain an upright posture. “The oldest indications for bipedality are found in Europe,” Böhme stated.
The researchers propose the bone belongs to Graecopithecus freybergi, an ape known from a jawbone in Greece, a tooth in North Macedonia, and a tooth at Azmaka. This species lived in a period when Europe hosted diverse apes, though most had vanished by 7.2 million years ago, leaving African apes as our closest relatives today.
Clément Zanolli from the University of Bordeaux in France, who was not involved, called it “a very, very beautiful discovery” due to its preservation, rare for Miocene hominid fossils. Yet he noted mixed features: some biped-like, others suggesting quadrupedal movement, complicating locomotor assessments.
Kelsey Pugh from OCAD University in Toronto agreed the association with Graecopithecus is tentative and emphasized that diagnosing bipedality from a single bone is challenging. Recent studies of extinct apes, including debates over the 7-million-year-old Sahelanthropus tchadensis from Chad, have raised standards for evidence, requiring multiple diagnostic traits.
Böhme's team has previously argued for European origins of hominin traits, citing Graecopithecus jaw features and the 11.6-million-year-old Danuvius guggenmosi, which could stand upright in trees. They suggest early hominins might have migrated to Africa amid climatic changes between 8.75 and 6.25 million years ago. Zanolli added that faunal movements between continents support such possibilities, but Pugh urged more Graecopithecus fossils to clarify relationships before detailed scenarios emerge.
The study appears in Palaeobiodiversity and Palaeoenvironments (DOI: 10.1007/s12549-025-00691-0).